Came around pretty much when she first showed up, what with shippers and them goin for any two characters that breathe next to eachother. Though funnily enough, the whole idea of her becoming Finn's protégé was talked about even back then, so it was nice to see that come about.
Also a lot of these threads take on Bron x Finn is mostly for the memes, lewds, and because its cute. I really doubt theyd make them a canon couple. Though id be fucking amazed and happy if they did.